This invention relates to railroad trackwork. More specifically, it relates to a frog of the spring rail type which is principally used at turn-outs from main line track.
A railroad frog is a device which is introduced at the intersection of two running rails to permit the flanges of railroad car wheels moving along one of the rails to pass across the other rail. The frog supports the wheels over the missing tread surface between the throat and the point of frog, and provides flangeways for the flanges of car wheels which pass through the frog.
Standard turnout frogs are generally either rigid frogs which have no movable parts or movable wing frogs in which one or both of the wings move outward to provide flangeways. A spring rail frog is a movable wing frog in which one of the wings moves outward to provide a flangeway. A spring rail frog is right-hand when the wing moves to the right looking from the toe toward the point of frog and left-hand when the wing moves to the left looking from the toe toward the point of frog. A spring rail frog is preferred over a rigid frog for turn-outs from a main line track. The reason for this is that a spring rail frog provides a practically continuous rail for the main line track and is smoother than a rigid frog.
A standard spring rail frog includes a rigid wing rail which is substantially aligned with a long point or heel rail connected to a turnout traffic rail and a movable spring wing rail which is substantially aligned with a short point or heel rail which is connected to a main line traffic rail. The rigid wing rail is connected at one end to a curved closure rail and the spring wing rail is connected at one end to a straight closure rail. The spring wing rail is spring biased against the long point rail and provides a substantially continuous support for the wheels of a car passing along the main line track. The spring wing rail is moved laterally away from the long point rail to provide a flangeway between the long point rail and the spring wing rail when a wheel of a car traversing the long point or rigid wing rail engages the spring wing rail and forces it to move laterally.
Spring rail frogs currently in use are interconnected with rail trackwork by mechanically connecting the long point and short point rails at the heel end of the frog with a turn-out and a main line rail, respectively, and by mechanically connecting the spring wing rail and rigid wing rail at the toe end of the frog with a straight closure rail and a curved closure rail, respectively. The end of the spring wing rail abutts the end of the straight closure rail to form a first joint and the two rails are mechanically connected. Similarly, the end of the rigid wing rail abutts the end of the curved closure rail to form a second joint and these two rails are mechanically connected. The first and second joints between the spring wing rail and the straight closure rail and the rigid wing rail and the curved closure rail are caled toe joints. One common mechanical connection for a toe joint includes a toe block having a base and a pair of lateral sidewalls. This connection is shown in American Railway Engineering Association (AREA) plan number 490-82. In that connection the toe block is positioned such that one lateral sidewall overlies the first toe joint and engages the inner sides of the webs of each of the spring wing rail and the straight closure rail. The other sidewall overlies the second toe joint and engages the inner sides of the webs of each of the rigid wing rail and the curved closure rail. A first joint bar overlies the first toe joint and engages the outer sides of the webs of the spring wing rail and the straight closure rail. A plurality of track and shoulder bolts pass through aligned bores in the one lateral wall of the toe block, in the spring wing rail web and in the first joint bar to thereby clamp the spring wing rail between the toe block and the joint bar. Track and shoulder bolts also pass through aligned bores in the toe block, the straight closure rail web and the first joint bar to clamp the straight closure rail between the first joint bar and the toe block. In this manner the spring wing rail is mechanically connected to the straight closure rail. Similarly, a second joint bar overlies the second toe joint and engages the outer sides of the webs of the rigid wing rail and the curved closure rail. A plurality of track bolts pass through aligned bores in the other lateral wall of the toe block, the rigid wing rail web and the second joint bar to clamp the rigid wing rail between the toe block and the joint bar. Track bolts also pass through aligned bores in the other lateral wall of the toe block, the web of the curved closure rail and the second joint bar to clamp the curved closure rail between the toe block and the second joint bar. In this manner, the rigid wing rail is mechanically joined to the curved closure rail. The function of the toe block in addition to providing a clamping surface for the rails is to maintain a specified angle between the spring wing rail and the rigid wing rail at the toe joint.
The spring wing rail must be movable laterally a distance of approximately two inches at the half inch point of frog when it is engaged by the flange of a car wheel traversing the long point rail or the curved closure rail to provide a flangeway for the wheel. To do this, the spring wing rail is hinged or pivoted at the first toe joint. In order to permit the spring wing rail to pivot at the toe joint a certain amount of clearance between the first joint bar and the spring wing rail web is provided. Additionally, the amount of clearance between the joint bar and the web of the spring wing rail must increase as the distance from the toe joint increases. This is obvious since the lateral movement of the spring wing rail along its length will increase from zero at the toe joint to 2 inches at the half inch point of frog. A plurality of stops, hold downs, and horns and a spring box are spaced laterally along the length of the spring wing rail and are positioned to prevent the spring wing rail from moving laterally more than two inches at the half inch point of frog. The spring box biases the spring wing rail tightly against the long point rail. It is adjusted so that approximately 700 pounds of force applied laterally to the spring wing rail by a rail car wheel flange at the half inch point of frog will cause the rail to move two inches at that point. The horns also provide a vertical restraint for the spring wing rail.
A disadvantage with a bolted mechanical toe joint which connects the spring wing rail with the straight closure rail is that such a joint because it must allow the spring wing rail to pivot provides little resistance to vertical movement of the spring wing rail. Thus, numerous vertical hold downs or horns are required in order to prevent vertical movement of the spring wing rail. A second problem with the bolted toe joint is that it causes a relatively rough ride as a rail car traverses the frog. One reason for this is that the spring wing rail must be relatively short in order to prevent its being so heavy that a spring box cannot generate sufficient force to maintain the movable end of the rail in contact with the long point rail with sufficient force. A short rail interrupts the natural frequency of the track. If the force of the spring box necessary to maintain the spring wing rail in contact with the long point rail becomes too high, it may actually deform the rail when it is engaged by a car wheel which is undesirable. However, a high force biasing the spring wing rail against the long point rail is desirable to ensure that debris such as rocks trapped between the spring wing rail and the long point rail do not prevent closure therebetween.
It is desirable to provide a spring rail frog in which the pivotal toe joint between the spring wing rail and the straight closure rail is eliminated. Additionally, it is desirable to provide a spring wing rail which will engage the long point rail with increased force without having to increase the force exerted on the rail by a spring box. Further, it is desirable to provide a spring wing rail of increased length to cooperate with the non-pivotal joint to provide a smoother ride for a wheel which traverses the frog.